1. Field of the Invention
The present invention relates to the field of monitoring the operations of devices used in fluid systems. More specifically, the present invention applies to the field of monitoring steam trap operation to detect and predict abnormal operation of the steam trap.
2. Description of the Prior Art
Typical steam-containing systems require that condensed fluids and some uncondensed gases be discharged from the steam to prevent system malfunction. To this end, a variety of devices have been employed to automatically discharge undesirable gases and condensate from steam-containing systems. These devices, referred to generally as steam traps, can operate in a variety of ways to perform the basic task of venting undesired gases and condensates from the steam system.
Failure of the steam trap in a steam system can produce serious system damage and loss. It is customary, therefore, to periodically monitor the operation of the various steam traps in the system to detect malfunctions of such devices and to identify abnormal operation that can indicate impending failure of the device.
In larger systems, the number of steam traps can be large, and the steam traps themselves may be difficult to access as well as to locate. Manual monitoring of steam traps can thus be difficult simply from the standpoint of locating a specific steam trap and then obtaining access to the steam trap once it has been located.
One manually operated prior art system used to evaluate steam trap operation, described in U.S. Pat. No. 4,898,022 to Yumoto et al., employs a monitor that must be handheld against the steam trap body to monitor vibration and temperature associated with the steam trap. The detected vibrations are compared with a standard baseline data set of vibrations representative of the type of valve being evaluated. Variations of the monitored characteristics from those in the standard baseline are indicative of abnormal operation of the monitored valve. The system is dependent, in part, upon the interpretive and manipulative skills of the operator, requiring the exercise of judgment as to the validity of the readings as well as requiring intimate and correct contact of the monitor with the valve being evaluated. The monitoring of this prior art system is not designed to be continuous for a particular steam trap and requires the physical presence of an operator at each steam trap during the monitoring.
In addition to the reliance on operator presence and skill, the Yumoto et al. technique suffers from the fact that the specific steam trap being monitored, even when operating properly, will not necessarily adhere to a xe2x80x9cstandardxe2x80x9d operating pattern in a particular environment. Moreover, as the environment of a steam trap changes, the operation of the steam trap may also change. Use of a representative xe2x80x9cstandardxe2x80x9d baseline data set for a particular type or model without proper regard to the steam trap operating environment and the operating history of the steam trap subjects the comparison of current operation data with such a xe2x80x9cstandardxe2x80x9d baseline data set to mistaken analyses.
Other prior art systems have also employed evaluation techniques in which the mechanism being monitored is tested against a baseline data set to provide information about the mechanism""s status or condition, or information about the system itself. Such systems are described, for example, in U.S. Pat. No. 5,154,080 to Hill et al., U.S. Pat. No. 5,535,136 to Standifer, and U.S. Pat. No. 5,206,818 to Speranza.
The Hill et al. system compares reflected ultrasonic signals and/or accelerometer signals against baseline data to evaluate check valve operation. Signals picked up by transducers placed externally on the valve are relayed by cables to a personal computer that processes the data to provide information about the valve.
The Hill et al. system employs baselines that are the results of tests and analyses previously performed on the valve assembly being evaluated. In this regard, the system is an improvement over the Yuunoto et al. technique, which uses representative baseline data. Inoperability or signs of wear of the valve using the Hill et al. system are determined by viewing computer results or viewing the data directly. An alarm is generated by the CPU when the values of certain monitored parameters exceed preselected levels. The Hill et al. system is not self-contained and does not provide an alarm or signal at the monitored component that identifies the location and condition of the component. The transducers and processing components required to implement the system are complex and expensive. As with the Yumoto et al. system, the Hill et al. system is not well-suited for continuous automated monitoring of valve operation.
The Standifer patent describes a technique in which an ultrasonic sound detector is used to accumulate data from known test leaks. The data is then compared with similar data from an actual system to quantify the leakage in the actual system. While the technique compares baseline data with on-line data for system evaluation purposes, individual control components in the system are not continuously monitored, and the condition or status of an individual control component is not automatically signalled by a self-contained monitor associated with the control component. The baseline data also is not used as an indication of normal operation, but is rather employed to provide a basis for quantifying the extent of leakage from the component or system.
The Speranza patent describes a system in which a portable monitor is taken to a xe2x80x9cfugitive emissionxe2x80x9d source to identify the source and quantify the emission. The monitor, which may be a single unit that includes a computer, is taken to the component to be monitored to perform a specific test. Results of the test may be stored in the computer, compared with other tests from the same component, and displayed on a computer screen. The Speranza system does not provide continuous monitoring and does not provide automatically generated signals associated with a specific monitored component to show the location of the component and to signal the status or condition of the component.
U.S. Pat. No. 4,945,343 to Rodriguez describes a system for continuously detecting malfunctioning of a steam trap and signalling malfunction of the trap. The system employs thermocouples at the input and output of a steam trap to sense malfunctioning of the steam trap. An alarm light is activated when a malfunction is detected. While the Rodriguez system offers the advantage of continuous monitoring, it provides an indication of component failure rather than an indication of abnormal operation of the monitored component. The alarm of the Rodriguez system is only activated when given preset conditions are met. No baseline comparisons are made in the system to evaluate evolving changes in the steam trap operation over its lifetime in the system.
The concept of xe2x80x9cstandardxe2x80x9d operation as a reference in continuously monitored systems is complicated by the fact that in the operation of a typical system, it is necessary to periodically shut down the system for either maintenance or repair or to modify the system design or operation. The sequence of shutting down and then restarting the system will produce a time-based operating change in the operation of the steam traps within the system. Such changes in system operation, when monitored by a system that employs only on-line operating conditions as the basis for establishing a standard baseline data set, may indicate abnormal operation of a steam trap that is in fact operating properly.
The system of the present invention employs a self-contained, continuously operating monitor to detect abnormal operation of a monitored component and to permit the taking of remedial action before adverse system operations occur. The monitor of the present invention is preferably adapted to be employed with a single control component in a specific operating environment. The operating characteristics of the monitored component, such as a steam trap, are compared with a specific baseline operating standard generated in the working environment, for the specific component being monitored and the condition or status of the monitored component is displayed at the component by an appropriate signal. In this regard, the monitor of the resent invention is physically associated with the monitored device to both directly display the device location and to signal the device""s operating condition. This feature of the system permits xe2x80x9cwalk-byxe2x80x9d surveillance of the component without the need for tracing alarm signals from a central monitoring point back to a specific component in the system and without the need for direct physical access to the component itself.
An important feature of the monitor and system of the present invention is that continuous monitoring of the monitored component is provided so that abnormalities are quickly detected as they develop. The system of the present invention also redefines xe2x80x9cnormalxe2x80x9d operation of the monitored component during the life of the component. Changes in system operation and component environment, and even changes in component operating characteristics, are considered in the operating program to continuously refine the normal baseline operating data set. The result is a faster and more accurate identification of abnormal operation or actual or impending malfunction of the monitored component.
An important object of the present invention is to define xe2x80x9cnormalxe2x80x9d operation for the monitored component to include start-up and shutdown sequences so that the system may be automatically reinitiated after a shutdown cycle without causing erroneous alert or malfunction alarms for the monitored component.
The monitor of the present invention is self-contained, can be easily moved from one monitored component to another, can be reprogrammed for use with a different component, is self-powered, and is independent of a connecting network with a central processing unit. The self-contained, on-site position of the monitor provides an immediate identification of the component being monitored with an immediate and continuous indication of the component""s operating status. Low power requirements, an efficient program and reprogrammable microprocessing circuitry within the monitor provide long life, portability, and versatility to the monitor.
The automated, self-contained features of the monitor of the present invention are independent of operator skill, operator presence, or operator intervention. The lack of reliance on operator interpretation and presence increases the speed, accuracy, and efficiency of the monitoring system of the present invention. Continuous monitoring of the control device produces immediate recognition of abnormal operation so that timely action may be taken to correct or prevent undesired operating conditions.
A preferred form of the present invention employs a simple, sonic transducer to detect malfunction of a disk-type steam trap. Using audible sounds as the monitored operating characteristic permits the use of low cost, compact, readily available audio-to-electrical transducers as the detecting mechanism for the monitor. When employed to monitor operation of a disk-type steam trap, the monitor of the present invention can immediately detect opening and closing cycles of the steam trap by detecting and analyzing the sonic events associated with the disk valve operation. The disk closure rate and changes in the closure rate are monitored and compared with data in an evolving signature baseline for the same steam trap. The status and condition of the steam trap is thus constantly being evaluated against an evolving xe2x80x9cstandard.xe2x80x9d Normal operations of the steam trap, as well as variations from the norm, are continuously signaled by appropriately colored lights that are readily visible to system inspectors.
From the foregoing, it will be appreciated that a primary object of the present invention is to provide a self-contained, continuously operating steam trap monitor that analyzes low frequency audio sounds emitted by the steam trap to detect and evaluate the steam trap performance and to form a visual signal representative of such performance.
Another object of the present invention is to provide a system in which a normal, baseline set of data for a particular system device can be established by a monitor associated with such device and to compare on-line operations of such device against the baseline data set whereby variations between such on-line operations and baseline data set can be employed to determine the operating condition of the monitored component.
An important object of the present invention is to provide a self-contained monitor that can be physically secured to a steam trap to provide continuous monitoring and status reporting of the condition of the steam trap. It is also an object of the invention to provide a readily discernible indication of such condition, such as by the illumination of different colored lights included as a part of the monitor whereby the condition of the monitor can be readily apparent to an inspector without the need for coming into physical contact with the steam trap or tracing the location of the steam trap from information obtained from a central monitor.
It is a general object of the present invention to provide a self-contained monitor having an internal battery power supply, microprocessor, and signal conditioner as well as differently colored light signals to convey continuous information regarding the condition or status of a steam trap.